Dehydration isn't something you wanna flirt with. The headaches are just the beginning! My dad recently suffered some serious dehydration (his ship sank at sea and he spent a couple days in a life raft) and his back pain was crazy from his kidneys being all "dude...where's the water?"
Water can be very boring, I agree. I've had good results when I drink with a straw (because I'm a five year old trapped in a 31 year old's body, maybe), and when I just park a big jug of it on my desk and try to get through it during the course of the work day. I also try to have a glass (not a big glass, just a cup or so) before a meal.
It gets easier

Just take it one cup or glass at a time.